This work deals with the Electrical Power System of the Lunar Rover, developed for the AMALIA mission, intended to compete in the Google Lunar X prize. The main subsystems are described and their operation analyzed on the basis of the observed experimental behavior. Primary generation is provided by triple-junction solar cells, arranged as four sections, each connected to a dedicated Array Power Regulator with separate Maximum Power Point Tracking. A Switch Matrix allows to rearrange the inter-connections among the Solar Array sections and the APR in order to manage possible failures. During load peaks and/or with low Sun elevation the solar array is supported by a secondary generator consisting of three redundant units with Li-Ion battery cells. Two alternate configurations of the Battery Subsystem were developed: a classical 8S Li-Ion battery, for a 28V Sun-regulated bus, and a novel approach, based on a single-cell (1S) Li-Ion battery and a high-voltage-gain Battery Charge-Discharge Regulator. A specific converter was designed for this configuration, based on the non-insulated Three Levels Neutral Point Clamped switching converter topology. Its correct operation with bus voltages up to 48V and fully discharged battery cells was demonstrated.